1. Field of the Invention
This invention relates to a collision preventing system for vehicles, including a detector for detecting an operational parameter between a subject vehicle and a contrast obstruction for judging the possibility of collision of the subject vehicle against the contrast obstruction, so that a brake is operated on the basis of a detection value detected by the detector.
2. Description of the Prior Art
Such collision preventing systems are conventionally well-known, for example, from Japanese Patent Publication No. 4700/86.
In the above prior art systems, each of the brakes is automatically operated when there has arisen a possibility of collision of the subject vehicle against a contrast obstruction, e.g., against a vehicle in front. However, the friction coefficient of the road surface is not taken into consideration and for this reason, a desired reduction in speed cannot be obtained on a road surface having a low friction coefficient, such as a snowy road or an iced road, even if full braking is applied. In addition, a vehicle driver cannot feel or sense automatic braking beforehand and, therefore, if such automatic braking is suddenly applied so as to avoid a collision, it imparts to the driver an impermissible braking feeling.